This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This core has the principle goal of developing protein localization methods for use with soft x-ray tomographic imaging. We will achieve this goal by further developing two approaches we have pioneered for labeling and visualizing molecules in cells, 1) Multi- modal imaging using fluorescence labels, such as GFP, and 2) using electron dense labels that can be seen directly in the soft x-ray image. A pivotal component of the multimodal approach is the use of high aperture cryogenic fluorescence microscopy, a new technology developed by the NCXT.